Process for preparing textile yarns



April 18, 1961 w. H. JAMIESON El'AL 2,980,492

PROCESS FOR PREPARING TEXTILE YARNS Fiied May 27, 1958 INVENTORSWILLIAM- H. JAMIESON CECIL E. REESE ATTORNEY United States Patent2,980,492 PROCESS FOR PREPARING TEXTILE YARNS William H. Iamieson,Newark, Del., and Cecil Reese, Kinston, N.C., assignors to E. I. du PontdeNemours and Company, Wilmington, DeL, a corporation of Delaware FiledMay 27, 1958, Ser. No. 738,032

13 Claims. (CI. 18-54) This invention relates to a novel process formanufacturing composite yarns having the property of becomingpermanently bulky when heated under controlled con- -ditions. Moreparticularly, this invention relates to a been made to produce a bulkycontinuous filament yarn in order to combine the desirable aestheticproperties of staple yarns with the advantages of continuous filamentyarn, such as strength and simplicity of processing. Thishas beenaccomplished in various ways by producing continuous filament yarns inwhich the various filaments 0on tained in a short segment of a yarn havedifferent lengths when straightened out. 1 V

It has been found that, when continuous filament yarn is treated so thatit becomes bulky and is then converted.

into fabric, some of the processing advantages of the originally smooth,dense continuous filament yarn are lost. This is due to the fact that inthe bulky yarn the yarn bundle is not compact, so that the filaments aresomewhat loose and have a tendency to snag as the yarns contact eachother or contact various parts of the yarn processing equipment. This isparticularly true during weaving or knitting. There is also a tendencyfor the bulky yarn to be pulled out into a smooth yarn bundle inresponse to tensions imposed by the yarn processing equipment, since ineach segment of the yarn the longer filaments which provide the bulkingeffect remain free of tension while the shorter filaments support theload imposed on the yarn; For these reasons a continuous filament yarnhas been desired which can be processed in its smooth, com-- pact forminto fabric and subsequently treated to obtain a satisfactory amount ofbulkin fabric form.; 1

' Composite continuous filament yarns comprised of filaments havingdifferent levels of shrinkagehave been'described in the prior-art. .Suchyarns can be woven into fabrics and subjected to shririking toachievebulking in fabric form owing to diflerential shortening of the lengthsof the filaments inthe. ;yai'ns, especially whenthe construction of thefabric is loose enough to permitthe yarns to shrink under little ornorestraint. Composite. convtinuous'filament yarns composed offilamentswhich-fm-ay f be caused to undergo spontaneous and irreversibleextension in length in varying amounts may be used even moreadvantageously, since the ability of the filaments to ur1- dergospontaneous extension in length is not influenced 2,980,492 PatentedApr. 18, 1 961 by fabric construction. Similarly, composite continuousfilament yarns having good bulking properties are advantageously formedby combining spontaneously and irreversibly extensible .filaments withshrinkable filaments, or with filaments'which exhibit little or nochange in length when they are heated or subjected to other processingconditions.

In the production of yarns capable of becoming bulky by differentialchange in length of the component strands upon heating or otherappropriate treatment, it has been regarded as necessary in the past toply together two different yarns, or otherwise associate together theirfilaments in some manner. Such a process has the disadvantage thatnumerous steps are required; i.e., the'yarns must be produced separatelyand selected according to their physical properties, following which theadditional 7 object is to produce such a yarn directlyby extruding ausually employed. It is step of plying or otherwise associating the,yarns is required. g

It is, therefore, an object of this invention to provide a novel processfor producing a composite yarn which has the property of becoming bulkywhen heated. Another molten polyester from a spinneret, and subsequentlydrawing the resulting yarn bundle, if desired. A further object is toprovide such a process which is readily adaptable for the preparation ofyarns which can be made to become bulky by differential shrinkability,difierential extensibility, or mixed shrinkability and extensibility.

The objects of this invention are accomplished by a process whichcomprises extruding a molten linear condensation polyester through aplurality of spinneret ori fices at unequal rates of flow to form solidfilaments of at least two different sizes and forwarding the filamentsso formed as a single filament-bundle, the-rates of poly: mer flow andthe rate of forwarding being adjustedso that in the filament bundle thespun denier 'per filament of the filaments of smallest size is not morethan about 8 and the ratio of the maximu'm'filament size to the minimumfilament size is at least about. 1.25. The forwarding speed may beselected within a wide range, forwarding speeds in excess of about 300yards per minute being generally desired that the extruded filaments beoriented to cause them to become tenacious. This may be done simply bywinding the extruded filaments at very high rates of speed, e;g., atabout 3000p about 5200 "yards per minute, as :described'by Hebeler inUS. Patent 2,604,689. Alternatively, the ex truded filaments maybe-wound up'in a yarn bundle and .then oriented by cold drawing the yarnup to about five;

times its original length in one ,or more separate steps, as disclosedby Whinfield and Dickson in U;S. Patent 2,465,3l9.-- Because theorientation of the yarn in the spinning step increases with spinningspeed, the draw ratio required to reach a given levelof orientation inthe yarn decreases as the spinning speed increases.

When the linear -condensation-polyester filamentsare spun and wound uptogether in a single yarn bundle in themanner described above, 'the yarnhas the smooth anddense characteristics of-a typicalcontinuousifilamentyarn; i.e.,- all ofthe filaments inia essentially freefrom loops orkinks The yarn may then fabrics areheated freefrom'tension, theyibeco'memerit yarns. Surprisingly, however, when these yarn s or given yarnsegment i have substantiallythe same length and'the filaments are.

bulky and voluminous. The bulking effect results from the differentialchange in length response of the various filaments to the heattreatment. In yarns prepared by the process of the invention asdescribed thus far, the diflerential response of the filaments to heattreatment is differential shrinkage; however, as described in detailbelow, the yarns are readily modified by preliminary heat treatmentunder controlled conditions so that the filaments exhibit differentialspontaneous extension in length or mixed shrinkage and spontaneousextension.

In yarns made in accordance with the process of the invention, thedifierence in length of the filaments in a given yarn segmentafter thefinal heat treatment amounts to at least about 5% of the length of thefilaments prior to the final heat treatment. Yarns composed of filamentshaving less than about 5% length differential, such as may be preparedby various methods, approach the relatively low bulk characteristics-ofstandard continuous filament yarn. When very high bulk is desired, theprocess of the invention may be used to provide yarns having a lengthdifferential of 30% or even higher. The differ'ential response to heattreatment can be'observed in the yarn extruded and wound up inaccordance with the process of the invention as described even in theabsence of a drawing step. However, the effect may be frequentlyincreased by the drawing step or by orienting the yarn by winding it athigh speed in the extrusion step.

In one embodiment of the invention, the total shrinkage of yarn isreduced by a preliminary heat treatment. In this embodiment, a moltenlinear condensation polyester is formed into oriented solid filaments ofat least two different sizes by extruding the molten polyester through aplurality of spinneret orifices into a fluid medium, e.g., air or anaqueous medium, and orienting the filaments so formed, the extrudedfilaments being wound in a single yarn bundle and the rates of polymerflow and the rate of winding being adjusted so that in the filamentbundle the spun denier per filament of the filaments of smallest size isnot more than about 8 and the ratio of the maximum'filament size to theminimum :filament'size is at least about 1.25, following which thebundle of oriented filaments is heated by passing it tures of- 150 C.and above.

through a zone maintained at a temperature of at least about 90 C. to":effect a shrinkage in the yarn not exceeding' the maximum shrinkage ofthe smallest denier filaments and passed. out of said zone and cooledbefore the yarnis fully crystallized. This is readily accomplished,since the rate at which the yarn relaxes orshrinks is much fasterthan-the rate:atwhichcrystallinity develops in the yarn. ,Of course,thetemperature and exposure timein the heatedzone should be such thatthe polymer does not melt or decompose. The orientation of the extrudedfilaments may be accomplished by winding them at high rates of speed, orin a separate drawing step, as previously described. Preferably, theyarn is maintained substantiallyamorphous or at only a low level of,crystal-' linityv throughout the orientation step and in the prelimmary.heating step Crystallinity is -minirnized in the orientation stepbyoperating at low temperatures, such as by drawing the yarn in thepresence of Water, and by orienting the yarn to a moderate degree only.'-In addition, rapid cooling following the drawing stepwill tend tolimit crystallization; In the preliminary heating step, cr'ystallinityis minimized bypassing the yarn through the heating zone as quickly aspossible consistent with the processing advantages of the continuousfilament yarn are thereby retained.

In a preferred embodiment of the process of the invention, a shrinkageof at least about 20% is effected in the yarn in the preliminary heattreatment described above, the crystallinity of the yarn preferablybeing maintained at a minimum level, as described. By effecting asufficiently high shrinkage, a minimum of at least about 20% usuallybeing required, at least some of the filaments comprising the yarnbecome spontaneously and irreversibly extensible, the spontaneousextension in length being achieved when the yarn is subjected to a finalheat treatment at any desired stage in the processing of the yarn.Surprisingly, the difierentialrespon-se of the filaments in the yarn toheat treatment is retained, and a high degree of bulk may be achievedwith these yarns containing spontaneously and irreversibly extensiblefilaments. Depending uponthe shrinkage level efiected in the preliminaryheat treatment, some of the yarns may become spontaneously extensiblewhile others remain shrinkable, or all of the filaments may becomespontaneously extensible in varying amounts.

The final heat treatment used to cause the yarns to become bulky may becarried out at any'desired time. As mentioned previously, :it isgenerally preferred'to employ this treatment after thefyarns have beenconverted into fabric form, although if desired the treatment may beused at an earlier stage of processing. An aqueous bath at the boil isusually a satisfactory medium for bulking the yarns, although in somecases aqueous baths at temperatures as low as 70 C. may be used. Dryheat, such as hot air, may also be used, especially at tempera- Theduration of the final heat treatment is sufiicient to allow-the yarn tobecome crystalline, in contrast to the brief duration'of the preliminaryheat treatment (if any), in whichit is usually desired to minimizecryst-allinity. For any given heating ture, however, so that the heattreatment used to achieve the bulkingeffect need not be carried outWithin a limited time after the yarns are prepared.-v It is onlynecessary to observethat the yarns are not subjected to temperatures inexcess of about 70 C. during slashing or other yarn processing stepsbefore the bulkiness in the yarns is desired. Moreover, once the yarnsare bulked, they remain stable and do not return to their original formwhen cooled or dried, assuming of course that they are not subjected totension high enough to stretch the shorter filaments in the yarn bundle.In some cases, if the yarn is heated at a temperaturein excess of theoriginal heat treatment used to achieve bulking, however, the degree ofbulk may actually increase to some extent. The heat treatment which isused to effect bulking inthe yarn can usually be carried out in waterat. 70 C. tolOO" C. even ifa preliminary; heat treatment .is used inprocessing the obtainirigthedesired shrinkageat the giventempera'ture. I

this preliminary heat treatment, the yarn is still characterized bydifferential response of the filaments to'further heat treatment,- and'such, treatment accordingly causes it the "filaments in the yarn andthis shrinkagelevel "is not Although the total shrinkage of the yarn isreduced'in I exceeded, the yarn bundle 'remzaas smooth and dense and 5':

yarn to reduce the shrinkage level of theyarn or to cause a some or allof the filaments therein ,to taneously extensible.-

The process of the present invention appears toclepend critically; uponthe nature of" the polymer employed. In generaL; the process appears to;be operable only with linear condensation polyesters, especially whenstable yarns are desired'which willgbulk up only when vgiven 'a specifictreatment as described herein rathertha'nunstable yarns which may =bulkup.pr' ematurely. Ina preferred embodiment of theinve'nti'on, alinearterephthalate polyester is'employed. By linear terephthalate polyester.is

become spon- V meant linear polyesters iii-which at least about 75% ofthe recurring stuctural'units' are units of the formula neret.

filaments of each group, is controlled] The necessary wherein Grepresents -a divalent organic radical containing from 2 to 12 carbonatoms and attached to the adjacent oxygen atoms by saturated carbonatoms. I Thus, the radical G may be of the form CH A CH where m is 0 or1 and A represents an alkylene radical, a cycloalky-lene radical, abis-alkylene ether radical, or other suitable organic radical. Thelinear terephthalate polyesters may be prepared by reacting terephthalicacid or an ester-forming derivative thereof with a glycol, G(OH) where-G- is a radical as defined above, to form the bis-glycol ester ofterephthalic acid, followed by polycondensation at elevated temperatureand reduced pressure with elimination of excess glycol. Examples ofsuitable glycols include ethylene glycol, diethylene glycol, butyleneglycol, decamethylene glycol, and trans-bis-1,4- (hydroxymethyl)cyclohexane. Mixtures of such glycols may suitably be used to formcopolyesters, or small amounts, e.g. up to about 15 mol percent, of ahigher glycol may be used, such as a polyethylene glycol. Similarly,copolyesters may be formed by replacing up to about 25 mol percent ofthe terephthalic acid or derivative thereof with another dicarboxylicacid or ester-forming derivative thereof, such as adipic acid, dimethylsebacate, isophthalic acid, or sodium3,5-dicarbomethoxybenzenesulfonate. Linear terephthalate polyesters andcopolyesters are especially suitable for use in the present inventionsince they have high melting points and since the crystallinity andorientation of filaments formed from them may be readily control-ledover a wide range.

If desired, the plurality of extruded filaments may be of a range ofsizes, subject to the limitation that the denier of the filaments ofsmallest size is not more than about 8 spun denier per filament and theratio of the maximum filament size to the minimum filament size is atleast about 1.25. However, only two filament sizes need to be used. Withrespect to the critical limitations of the smallest size filaments andsize ratio, it has been found that it is not possible to obtain adifferential change in length of at least 5% throughout the rangespecified when the smallest filaments are larger than about 8 denier.

The filaments may also have a variety of cross-sections. In addition tousual round cross-section, shapes which may be used include cruciform,asterisk, Y, ribbon, zigzag, and keyhole cross-sections. Suchcross-sections may be achieved by extruding the filament throughanorifice of appropriate shape formed by intersecting slots or holes, orby extruding a plurality of small filaments from a pattern of round ordiamond-shaped holes spaced sufficicntly close together that theextruded filaments coalesce in the desired pattern. When more than onefilament cross-section is employed in extruding filaments in accordancewith the present invention, it is preferred that the larger denierfilaments be of round cross-section or of more nearly, roundcross-section than the smaller denier filaments; i.e., it is preferredthat the cross-section of the larger denier filaments have a smallerratio of permiter to diameter than the cross-section of thesmaller-denier filaments. V i

This invention will be further illustrated by reference to theaccompanying drawing in which: l-

Figure 1 is a schematic representation of suitable apparatus utilizing adivided pack spinneret; and

Figure 2 is a fragmentary cross-sectional view of a spinneret plate andmetering plate of aisingle, pack spin- Referring to Fig. l, the base ofa' portion of a spinneret assembly is represented by reference numeral11. Wall 12 divides the spinneret into two separate cavities material 15resting .on screen assemblies 16 and 16.

forming two groups of filamentsil-S and19. By using different feed ratesto the cavities, the relative size-of the 13 and 14 which are filledwith a finely divided, inert Molten material,.meter,ed to cavities 13and 14 spin-QT ning pumps not shown, is extruded through; orifices 17,

rates of polymer How are readily calculated from the number of fialmentsdesired of each size, the size or In carrying out the process of thepresent invention,

the filaments may also be extruded from-separate spinnerets arranged inside-by-side relationship, provided theyv are wound together at the samerate in a single yarn bundle in a manner similar to that shown in Fig.1.

The filaments may also be extruded from a single pack through a singlespinneret plate containing orifices of different diameter to achiveunequal rates of polymer flow and thereby form filaments of dilierentsizes due to the difierential pressure drop through the variousorifices. However, when this method is used, some experi mentation maybe necessary to achieve the desired range of filament sizes. i

As shown in Fig. 2, a metering plate 23 in contact with a spinneretplate 24, containing capillary holes 25 and 2.6 aligned with thespinneret orifices '27 may be used to deliver molten polymer to thespinneret orifices at unequal rates of fiow, the diameter of thecapillaries in the meteringplate being varied to the extent sufficienttoprovide thedesired rates of flow through the various orifices. I

The ex ression oriented filaments is used herein to denote filamentshaving a birefringence of .at least about 0.0 4. The birefringence,-ordoublerefraction, of polymeric filaments is primarily dependent upon theorientation of the polymer molecules along the'axis of the filament andis a convenient measure of suchorientation.

Thebirefringence, which is also called the specific index 7 ofbirefringence, may be measured by the retardation technique described inFibres From Synthetic Polymers by R. Hill (Elsevier Publishing Company,New York, 1953), pages 266-8, using a polarizing microscope withrotatable stage together with a cap analyzer and quartz wedge. Thebirefringence is calculated by dividing. the

measured retardation by the measured thickness of the structure,expressed in the same units as the retardation. The intrinsic viscosityof the polymer is used herein as a'measure .of the degree ofpolymerizationof the polymer and maybe defined as I limit as-Capproaches!) wherein 1;,is the viscosity of a dilute solution of thepolymer in a solyent divided by ,the viscosity of the solventperse'measu'red in the same unitsat the same temperature; and C is theconcentration in grams of the polymerper ml. of solution. Fomal, whichcomprises 58.8 parts by weight of phenol and 41.2 parts by weight oftrichlorophenol, is a convenient solvent for measuring theintrinsicviscosity of linear polyesters, and intrinsic iviscosity values reportedherein are with reference to Fomal as a solvent.

The, expression spont aneous extensibility? s used hereinto denoteextension in lengthunder zerotension,

that is, without external force being applied.

The following exam'pleswill serve to further illustrate the inventionand are not intended to be construed as limitative, 1 1 j n V EXAMPLE 1;1:

' Polyethylene terephthalate having "an intrinsic-lvisc'osity C.

from a divided pack through a spinneret having 27 round orifices, each0.009 inch in diameter, 7 of the orifices being on one side of the packand 20 of the orifices being on the other side of the pack. Moltenpolymer is metered at equal ratesseparately from each side of thedivided pack to the spinneret. The yarn is wound up together as a singlefilament bundle at a speed of 1200 yards per minute and is found to havea denier as spun of 200. The yarn accordingly comprises 27 filaments ofround cross-sections, 7 having a spun d.p.f. (denier per filament) of14.2 and 20 having a spun d.-p.f. of 5.0. A sample of the spun yarn,when placed in a bath of 100 C. water for five minutes, shrinks andbecomes quite bulky. By separating the filament bundle and measuringindividual filaments before and after immersion in 100 C. water, it isfound that the 14.2 d.p.f. filaments shrink only 40%, while the 5.0d.p.f. filaments shrink 51%. The diiferential shrinkability accordinglyamounts to 11%.

The yarn is passed from a supply package through a bath of water at 25C. and over a sponge to leave a thin uniform film of water on the yarn,after which it is passed around a feed roll, around a draw pin 1.6inches in diameter maintained at a temperature of 100 C., and thenaround a draw roll, finally being wound up on a suitable package. Thespeed at the draw roll is 454 yards per minute and the draw ratio is3.113. A sample of the drawn yarn, when immersed in a bath of water at100 C. for five minutes, is also found to become quite bulky. Byseparating the filament bundle and measuring individual filaments beforeand after immersion in 100 C. water, it is found that the larger denierfila ments shrink 43%, While the smaller denier filaments shrink only33%, corresponding to a diiferential shrinkability of 7 In anotherexperiment, the yarn is drawn as indicated above, except that the drawnyarn is passed continuously 'fromthe draw roll through a chambercontaining steam maintained at 100 C., returned through the steamchamber on a second pass, and then wound up on a suitable package. Theyarn path through the steam measures 12 inches on each pass. The yarnspeed at the draw roll is 454 yards per minute as before; however, therate of winding is only 318 yards per minute, corresponding to a 30%shrinkage of the yarn on passage through the steam chamber. The exposuretime of the yarn to the steam is 0.125 second, based on the rate ofwithdrawal of the yarn from the chamber on the second pass. when drawnand heattreated in this manner, is again found to become quite bulkyv onimmersion in 100 C. water for five minutes. By separating the filamentbundle as before, it isfo-undthat the larger denier filaments shrink13.9% and the smaller denier filaments only 2.6%, cor-.

.up speed being 270 yards per minute, corresponding to a shrinkage of40.5% and an exposure time 0130.147 second. Immersion of the"drawn andheat-treated yarn in 100"C.'Water-for'five minutes results in 3.1%shrinkage in the larger denier filaments and 5.0% extension in length inthe smaller denier filaments, a differential length change of,8.l%based'on the length of the yarn prior to immersion in water.

In a similar pair of jexperinients a draw ratio of 2.852

The yarn,

It is found that, upon immersionof the.

7 minute.

' the 'othrQside of the pack. Molten polymer ismetered;

' T pack to the spinneret. The yarn is wound upgtogether as is used and,when the drawn yarn is immersed in C.

waterforfive minutes, the larger denier filaments shrink 54% theisn'i'allerdenier filaments 36% correspondf 8. ing to a ditferentialshrinkage of 18%. In one of the experiments, the yarn drawn at a ratioof 2.852 is passed continuously through a steam chamber in the mannerdescribed above, the windup speed being 270 yards per minute,corresponding .to a shrinkage of 40.5% and an exposure time of 0.147second. Immersion of the drawn and heat-treated yarn in- 100 C. waterfor five minutes results in 2.0% extension in length in the largerdenier filaments and 9.2% extension in length in the smaller denierfilaments, a differential length change of 7.2%.

EXAMPLE II Polyethylene terephthalate having an intrinsic viscosity of0.59 and containing 0.3% TiO is spun at 295 C. from a divided packthrough a spinneret having 27 round orifices, each 0.009 inchindiameter, 7 of the orifices being on one side of the pack and 20 ofthe orifices being on the other side of the pack. Molten polymer ismetered at equal rates separately from each side of the divided pack tothe spinneret. The yarn is wound up together as a single filament bundleat a speed of 1200 yards per minute and is found to have a denier asspun of 138. The yarn accordingly comprises 27 filaments of roundcross-section, 7 having a spun d.p.f. of 9.9 and 20 having a spun d.p.f.of 3.45. The yarn is passed from a supply package through a bath ofwater at 25 C. and over a sponge to leave a thin, uniform film of wateron the yarn, after which it is passed around a feed roll, around a drawpin 1.6 inches in diameter maintained at a temperature of 92 C.,-andthen around a draw roll, the draw ratio being 2.609 and the speed at thedraw roll being 227 yards per The drawn yarn is passed continuously fromthe draw roll through. a chamber containing steam maintained at 100 C.,the-coutact distance with the steam being 9 inches, and the yarn is thenwound up on a suitable package. The rate of winding is only yards perminute, corresponding to a 40.5 shrinkage of the yarn on passage throughthesteam chamber. The exposure time of the yarn to'the steam is 0.111second, based on the rate of withdrawal of the yarn from the chamber.The resulting yarn has a tenacity of 1.7 grams per denier and a breakelongation of When a sample of the yarn is immersed in water at 100 C.for five minutes, it is found to exhibit a spontaneous extension inlength of 3.0%. By separating the filament bundle and measuringindividual filaments before and after irmnersion in 100 C. water, it'isfound that the larger denier filaments exhibit a'spontaneous extensionin length of 3.3% and the smaller denier filaments exhibit a spontaneousextension in length of 8.3%, adifierential length change of 5.0% basedon the length of the yarn prior to immersion in water. g v I Aquantityofthe steam-relaxed yarn is woven into, a 135-sley, l'20-pick, 2xZbasket weave fabric. Temperatures in 'exces's of 70 C. are avoided inslashing and otheryarn. processing steps. The woven fabric is smooth andhas the characteristic slick hand of continuous filament syntheticyarns; however, after immersionin 100 C. water for five minutes thefabric develops a desirable soft hand with increased cover and opacity-EXAMPLE III Polyethylene terephthalate having an intrinsic viscosity of0.57 and containing 0.3% 'TiO is spun at 295 C. from a divided packthrough a spinneret having 11 round on"- fices, each 0. 006 inchindiameter, on one side'of the pack and 27 Y-shaped orifices, eachwmprising three intersec'ting slots 0.003 inch wide and 0.025 'inchlong, on

at equal'rates separately from each'side ofthe divided a singlefilament. bundle at a speed of 1200-yards per minute and isfound to havea denier as spun of 208. -The yarn accordingly comprises 11 filaments-ofround crossse'c'tion having a spund p'ifi of about-9.5 and 27 filamentsof Y-shaped cross-section having a spun d.p.f. of about 3.9 The yarn ispassed from a supply package through is then passed from a feed rollthrough a hollow needle leading into a nozzle having a throat diameterof 0.062

inch and a 7 flared exit passage and thence to asuitable windup package.Air is maintained at 220 C. and p.s.i. pressure on the entrance side ofthe nozzle, so that a jet of hot air is caused to fiow through thenozzle in the same direction as the yarn is passed through the nozzle.The tip of the hollow needle from which the yarn is delivered is locatedwithin the throat of the nozzle and the efiective distance through whichthe yarn is heated is 1.35 inches. The yarn is passed into the nozzle at302 yards per minute and wound up at 150 yards per minute, correspondingto a shrinkage of 49.6% and an exposure time of 0.015 second, based onthe rate of withdrawal'of the yarn from the nozzle. The yarn prepared inthis way is a composite yarn which becomes quite bulky after immersionin 100 C. water for five minutes. By separating the yarn bundle andmeasuring individual filaments before and after immersion in 100 C.water, it is found that the filaments which have a Y-shapedcross-section exhibit a 14% spontaneous and irreversible extension inlength in the boiling water, while the round-shaped cross-sectionfilaments exhibit a shrinkage of in the boiling water.

A quantity of the air-jet relaxed composite yarn is woven into a120.-sley, 114-pick, 2 x 2 basket weave fabric. Temperatures in excessof 70 C. are avoided in slashing and other yarn processing steps. Thewoven fabtic is smooth and has the characteristic slick hand ofcontinuousfilament synthetic fabrics; however, after immersion in 100 C.water for five minutes, the fabric exhibits a warm and soft hand andshows a marked increase in cover and opacity.

EXAMPLE IV passed into the oven at 400ffeet perminute and wound up. at180 feet. per minute, corresponding to a shrinkage of 55% and anexposure time of 0.333 second, based on the rate of withdrawal of theyarn from the oven.- The yarn prepared in this way is a composite yarnwhich becomes bulky after immersion in 100 C. water for five minutes. Byseparating the yarn bundle and measuring individual filaments before andafter immersion in 100 C. water, it is foundthat the filaments whichhave a Y- shaped cross-section exhibita 12% spontaneous and irreversibleextension in length in boiling water, while the round-shapedcross-section filaments exhibit a 3% extension in length.

A quantity of the steam-relaxed yarn is woveninto a 135,-sley,120-pi'ck, 2 x 2 basket weave fabric. Temperatures in excess of 70 C.are avoided in slashing and other yarn processing steps. The wovenfabric is smooth and has the characteristic slick hand of continuousfilament synthetic yarns; however, after immersion in- 100 C. water forfive minutes thefabric develops a warm 7 soft hand and shows a markedincrease in cover and opacity Y 1 EXAMPLE v' I Polyethylene.terephthalate having an intrinsic viscosity eras is spun'at 298.C.through aspinneret ha ving 1 4 and averaging 17.4 d.p.f., and 3filaments averaging 27.8 d.p.f. The yarn is drawn'3.4 over a 1.6 inchpin maintained at 101 C., the rate of winding in the drawing step being227 yards per minute. The drawn yarn accordingly comprises 4 filamentsaveraging 1.2 d.p.f., 7 filaments averaging 5.1 d.p.f., and 3 filamentsaveraging 8.2 d.p.f. The yarn is found to have a tenacity and elongationat maximum strength of 3.6 grams per denier and 19.6%, re-

spectively. The yarn prepared in this way is a composite yarn whichbecomes bulky after immersion in C. water for five minutes. Byseparating the filament bundle and measuring individual filaments beforeand after immersion in 100 C. water, it is found that the drawnfilaments averaging 8.2 d.p.f. shrink 15.0%, while the filamentsaveraging 1.2 d.p.f. shrink only 8.8%. The difierential shrinkabilityaccordingly amounts to 6.2%.

The experiment is repeated, except that the yarn is wound at 800 yardsper minute and the total spun denier is 262, the yarncomprising 4filaments averaging 5.1 d.p.f., 7 filaments averaging 21.6 d.p.f., and 3filaments averaging 30.2 d.p.f. The yarn is drawn as in the precedingexperiment, using a draw ratio of 3.92. The drawn yarn accordinglycomprises 4 filaments averaging 1.3 d.p.f., 7 filaments averaging 5.5d.p.f., and 3 filaments averaging 7.7 d.p.f. The tenacity and elongationat maximum strength of the yarn are 4.0 grams per denier and 25.0%,respectively. The yarn prepared in this way is a composite yarn whichbecomes bulky after immersion in 100 C. water for five minutes. Byseparating the filament bundle and measuring individual filaments beforeand after immersion in 100 C. water, it is found that the drawnfilaments averaging 7.7 d.p.f. shrink 15.6%, while thefilamentsaveraging 1.3 d.p.f. shrink only 9.8%. The differential shrinkabilityaccordingly amounts to 5.8%.

7 EXAMPLE VI Polyethylene terephthalate having an intrinsic viscosity of0.57 and containing 0.3% TiO is spun at 295 C. from a divided packthrough a spinneret having 27 round orifices, each 0.009 inch indiameter, 7.of the orifices being on one side ofthe pack and the other20 orifices beingon the other side of the pack. In a series ofexperiments, molten polymer is metered at various controlled ratesseparately from each side of the divided pack to th e spinneret toproduce 7 large filaments and 20 small filamentsin each yarn, thefilament sizes in each yarn being shown in Table I as'well as thedenier. ratio of the larger to the smaller filaments. The "yarn is woundup together as a single filament bundle at a speed In each case, thespun yarn of 1200 yards per minute. is passed from a supply packagethrough a bath of water at 25C. and over a sponge to leave a thin,uniform film of water on the yarn, after which it is passed around afeed roll, around a draw pin 1.6 inches in diameter maintained at atemperature of 100 C., and, then around a draw roll, finally being woundup on a suitable package. The speed at the draw roll is 100 yards perminute and the draw ratiois 3.0. The drawn yarn is then passed from afeed roll into a nozzle and exposed to a jetof hot air maintained at 220C. in the manner described in Example III. The 'yarn is passed into thenozzle at 250 yards per minute and wound up atyards per minute,corresponding to a shrinkage of 40% and an Qchange.

1 Negative figures indicate extension in length.

EXAMPLE VII A polyethylene terephthalate/S (sodium sulfo) isophthalate(98/2) copolyester having an intrinsic viscosity of 0.52 is prepared bya condensation reaction between 2.1 mols of ethylene glycol and amixture of 0.98 mol of dimethyl terephthalate and 0.02 mol of sodium3,5- dicar'oomethoxybenzenesulfonate in the presence of manganousacetate and antimony trioxide as catalysts, 0.3% by Weight of TiO beingadded to the reactants to deluster the polymer. The copolyester is spunat 295 C. from a divided pack through a spinneret having 85 roundorifices, each 0.009 inch in diameter, 17 of the orifices being on oneside of the pack and 68 orifices being on the other side of the pack.The yarn is wound up together as a single filament bundle at a speed of750 yards per minute and is found to have a denier as-spun of 400.

,The yarn accordingly comprises 85 filaments of round cross-section, 17having a spun d.p.f. of 11.8 and 68 filaments of round cross-sectionhaving a spun d.p.f. of 2.94. The yarn is then passed from a supplypackage through a bath of water at 25 C. and over a sponge to leave athin, uniform film of water on the yarn, after which it is passed arounda feed roll, around a draw pin 1.6 inches in diameter maintained at atemperature of 100 C., and then around a draw roll, finally being woundup on a suitable package. The speed at the draw roll is 333 yards perminute and the draw ratio is 3.57. The drawn yarn is then passed from afeed roll into a nozzle and exposed to a jet of'hot air maintained at220 C. in the manner described in Example III. The yarn is passed into.the nozzle at 250 yards per minute and wound up at 137.5 yards perminute, corresponding to a shrinkage of 45% andan exposure time of0.0164second. The product is a smooth, continuous filament yarn;however, whenit is placed in a bath of water at 100 C. for

' and after immersion in-l 0 C. water, it is found that the largerdenier filaments shrink 16%, While the-smaller denier filaments exhibita spontaneous and irreversible extension in length amounting to 8%. Thiscorresponds to a differential length change of 24%, based 'on the lengthof the yarn before treatment with 100 C; water.

In a rclated experiment, yarn is spun and drawn as describedabove,'except1that"a spinning speed of 1350 yards per minute is used. Asin the first experiment described in this example, the yarn isfed intothe air jet at 250 yards per minute and wound up at 137.5 yards perminute, corresponding to a shrinkage of 45% and an exposure time of0.0164 second. By separating the filament bundle and measuringindividual filaments before and after immersion in 100 C. water, it isfound that the larger denier filaments shrink 4% and the smaller denierfilaments exhibit a spontaneous and irreversible extension in length of12%, corresponding to a differential length change of 16%.

As indicated in the foregoing discussion, the filaments are extruded andare forwarded as a filament bundle by a common forwarding means. Inforwarding the filament bundle it will be apparent that many differentmeans may be utilized. In addition to winding the filaments on a commonpackage, they may be forwarded, e.g. by an air jet, to a containerwithout winding and thereafter withdrawn for further processing.

Many advantages over the prior art accrue from the present invention.Oneadvantage resides in the simplicity of the present process. The yarnsare handled as a continuous filament bundle, thus substantially reducingthe tendency toward snagging in various processing operations. Thenecessity for plying different filaments together to produce bulky yarnsis eliminated as well as the numerous steps required in preparing andselecting filaments having different physical characteristics. One ofthe primary advantages resides in the fact that bulking may be producedafter the yarn has been woven or knitted into a fabric, e.g., as thefabric is passed through a hot dye bath. This eliminates the tendency ofthe bulky yarn to be pulled out into a smooth yarn bundle when subjectedto tension during the knitting and weaving processes.

Throughout the specification and claims, any reference to parts,proportions and percentages refers to parts, proportions and percentagesby weight unless otherwise specified.

It will be apparent that many widely different embodiments of thisinvention may be made without departing from the spirit and scopethereof, and therefore it is not intended to be limited except asindicated in the appended claims.

We claim:

1. A process for preparing textile yarn having the property of becomingbulky when heated to a temperature from about 70 C. to about 220 C.which comprises forming a filament bundle consisting of at least twospecies of continuous essentially straight-filaments of equal length byextruding a molten linear condensation polyester through a plurality oforifices at unequal rates of flow and forwarding said filaments as acontinuous about 5200 yards per minute.

filament'bundle, the rate of flow through said orifices and the rate offorwarding being adjusted so that the first of said species has a denierof not greater than about 8 and anotherof said species has adenier atleast 125 times the denier of said first species, maintaining a both ofsaid species as separate essentially. straight continuous filamentarystructures throughout said forwardmg step. i

2. The process of claim 1 a linear terephthalate polyester.

3. The process of claim lwherein said filaments are oriented bywithdrawing them from said'orifices and windwherein said polyester ising them in" continuous filament form onto .a common package at is ratefrom about 3000 yards permin'ute to 4. A process for preparing textileyarnhaving the property of becoming bulky when heatedtoa temperaturefrom about 70 C.'to about 220 C. which comprises forming a filam cntbundle consisting of at 'least two spe cies of continuous essentiallystraight filaments" of equal length by extruding a molten linearcondensation polyester through a plurality. of orifices at unequal ratesof flow, forwarding said filaments as a continuous filament bundl'ftherate of flew throughisaid orific'es and'therate of forwarding beingadjusted so that the first of said species has a denier of not greaterthan about 8 and another of said species has a denier of at least about1.25 times the denier of said first species, and orienting saidfilaments by drawing them up to about five times their original length,maintaining both of said species as separate essentially straightcontinuous filamentary structures throughout said forwarding andorienting steps.

5. The process of claim 4 wherein said polyester is a linearterephthalate polyester.

6. A process for preparing textile yarn having the property of becomingbulky when heated to a temperature from about 70 C. to about 220 C.which com prises forming a filament bundle consisting of at least twospecies of continuous essentially straight filaments of equal length byextruding a molten linear condensation polyester through a plurality oforifices at unequal rates of flow, forwarding said filaments as acontinuous filament bundle, the rate of flow through said orifices andthe rate of forwarding being adjusted so that the first of said specieshas a denier of not greater than about 8 and another of said species hasa denier of at least about 1.25 times the denier of said first species,orienting said filaments by drawing them up to about five times theiroriginal length, maintaining both of said species as separateessentially straight continuous filamentary structures throughout saidforwarding, orienting and shrinking steps and thereafter shrinking saidoriented filaments an amount less than the maximum shrinkage of saidfirst species by passing them through a zone maintained at a temperatureof at least 90 C.

7. The process of claim 6 wherein said filament bundle consists ofessentially amorphous filaments and said essentially amorphous structureis maintained throughout the orienting and shrinking steps.

8. The process of claim 7 wherein said shrinkage is at least about 20%9. The process of claim 8 wherein said polyester is a linearterephthalate polyester.

10. A process for preparing textile yarn having the property of becomingbulky when heated to a temperature from about 70 C. to about 220 C.which comprises forming a filament bundle consisting of at least twospecies of continuous essentially straight filaments of equal lengthhaving an essentially amorphous structure by extruding a molten linearcondensation polyester through a plurality of orifices at unequal ratesof flow whereby the first of said species has a denier of not more thanabout 8 and another of said species has a denier of at least about 1.25times the denier of said first species,

' and the cross-section of the second of said species has a smallerratio of perimeter to diameter than the crosssection of said firstspecies, thereafter collecting said filament bundle while maintainingboth of said species as 14 separate essentially straight continuousfilamentary structures.

11. The process for preparing bulky yarn which comprises extruding amolten linear condensation polyester through a plurality of orifices atunequal rates of flow to form a filament bundle consisting of at leasttwo species of continuous essentially straight filaments of equallength, the first of said species having a denier of not more than about8 and the second of said species having a denier of at least 1.25 timesthe denier of said first species, thereafter collecting said filamentbundle while maintaining both of said species as separate essentiallystraight continuous filamentary structures, and thereafter heating saidfilaments while essentially free, from tension to a temperature fromabout C. to about 220 C. whereby the differential change in length ofsaid two species is at least 5%.

12. The process for preparing bulky yarns which comprises extruding amolten linear condensation polyester through a plurality of orifices atunequal rates of flow to form a filament bundle consisting of at leasttwo species of continuous essentially amorphous filaments of equallength, the first of said species having a denier of not more than about8 and the second of said species having a denier of at least 1.25 timesthe denier of said first species, orienting said filaments by drawingthem up to about five times their original length and shrinking saidoriented filaments an amount less than the maximum shrinkage of saidfirst species by passing them through a zone maintained at a temperatureof at least C. while maintaining said essentially amorphous structure,maintaining both of said species as separate essentially straightcontinuous filamentary structures throughout said extruding, orienting,and shrinking steps, and thereafter heating said filament bundle whileessentially free from tension to a temperature from about 70 C. to about220 C. whereby the differential change in length of said two species isat least 5%.

13. The process of claim 12 wherein said oriented filaments are shrunkat least about 20% References Cited in the file of this patent UNITEDSTATES PATENTS Great Britain Apr. 2,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.2,980,492 April 18, 1961 Wil'ilgiam H. Jamieson et a1;

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

. Column 5, line 42 after "to" insert the column 6, line 2, forfialments"- read filaments column 13, lines 26 to 29, strike out Hmaintaining both of said species as separate essentially straightcontinuous filamentary structures throughout said forwarding, orientingand shrinking steps"; same column 13 line 32, after "90 C." insertmaintaining both of said species as separate essentially straightcontinuous filamentary structures 6 throughout said forwarding,orienting and shrinking steps.

Signed and sealed this 2nd day of January 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID L. LADD A'it testing Officer Commissioner ofPatents

1. A PROCESS FOR PREPARING TEXTILE YARN HAVING THE PROPERTY OF BECOMINGBULKY WHEN HEATED TO A TEMPERATURE FROM ABOUT 70*C. TO ABOUT 220*C.WHICH COMPRISES FORMING A FILAMENT BUNDLE CONSISTING OF AT LEAST TWOSPECIES OF CONTINUOUS ESSENTIALLY STRAIGHT FILAMENTS OF EQUAL LENGTH BYEXTRUDING A MOLTEN LINEAR CONDENSATION POLYESTER THROUGH A PLURALITY OFORIFICES AT UNEQUAL RATES OF FLOW AND FORWARDING SAID FILAMENTS AS ACONTINUOUS FILAMENT BUDNEL, THE RATE OF FLOW THROUGH SAID ORIFICES ANDTHE RATE OF FORWARDING BEING ADJUSTED SO THT THE FIRST OF SAID SPECIESHAS A DENIER OF NOT GREATER THAN ABOUT 8 AND ANOTHER OF SAID SPECIES HASA DENIER AT LEAST 1.25 TIMES THE DENIER OF SAID FIRST SPECIES,MAINTAINING BOTH OF SAID SPECIES AS SEPARATE ESSENTIALLY STRAIGHTCONTINUOUS FILAMENTARY STRUCTURES THROUGHOUT SAID FORWARDING STEP.